Esters derived from benzoic acid and mono- and dihydric alcohols containing from 2 to 20 or more carbon atoms are known as plasticizers for a variety of both crosslinked and non-crosslinked organic polymers, including homopolymers and copolymers of esters derived from ethylenically unsaturated acids such as acrylic and methacrylic acids and homo- and copolymers of vinyl acetatel. The alcohol portion of these esters typically contains from 1 to 10 or more carbon atoms. These polymers can optionally include repeating units derived from ethylenically unsaturated hydrocarbons such as ethylene and styrene.
U.S. Pat. No. 5,236,987 to William Arendt, which issued on Aug. 17, 1993, teaches using certain esters of benzoic acid as coalescents and plasticizing agents for water-based paint compositions containing an emulsified acrylic polymer as the film-forming material. The alcohol portion of the benzoic acid ester contains from 8 to 12 carbon atoms and the polymer is typically present in the composition as an aqueous emulsion.
The major ingredients of the paints described in the Arendt patent typically comprise a water borne film-forming polymer derived from at least one ester of acrylic and/or methacrylic acid, water, a pigment, a thickening agent and at least one surfactant. The combination of pigment and thickening agent typically constitutes from 20 to 50 percent by weight of the total paint composition.
Film-forming compositions such as inks, adhesives and floor polishes contain different ingredients and types of film forming polymers than paints. Even though the polymers in these compositions are prepared from the same class of monomers as those present in paints, the type(s) of monomer(s), the molecular weight of the polymer, and the presence and interaction of the additional ingredients present in the various types of compositions make it difficult to predict how a coalescent, leveling agent and/or plasticizer suitable for use paint compositions will affect the properties of other film-forming compositions, such as adhesives and polish formulations, and the properties of the resultant films.
European Patent No. 668,338 issued to Rohm and Haas describes adhesive compositions wherein the film-forming material is an acrylic polymer. In addition to the polymer the compositions also include from 0.1 to 40 parts by weight per 100 parts of polymer of a plasticizer. Suitable plasticizers include benzoic acid esters derived from diethylene glycol and/or dipropylene glycol. No benzoate esters derived from aliphatic alcohols are disclosed.
Classes of compounds disclosed as being effective coalescing, leveling, and/or plasticizing agents for compositions containing polymerized ethylenically unsaturated esters as the film-forming polymer include but are not limited to organic esters such as dioctyl adipate and 2,2,4-trimethyl-1,4-pentanediol mono- and diisobutyrates, esters of phthalic acid wherein the alcohol portion of the ester typically contains from 3 to 10 carbon atoms, partially etherified diols and triols such as 2-(2-ethoxyethoxy)ethanol, and trialkoxyalkyl phosphates such as tributoxyethyl phosphate. Some of these materials, particularly esters derived from aliphatic carboxylic acids such as adipic acid, do not substantially improve either the film-forming properties of aqueous polymer compositions typically used as adhesives, inks, floor polishes and unpigmented coatings, or the appearance of films formed from these compositions.
U.S. Pat. No. 6,989,830, which issued to William D. Arendt et al. on Feb. 10, 2004 describes film-forming compositions, including floor polishes, containing 1) at least one acrylic, vinyl acetate or epoxide polymer or copolymer as a film-forming ingredient and 2) an ester derived from benzoic acid and a monohydric alcohol containing 8 carbon atoms. The alcohol is preferably 2-ethylhexanol. These benzoic acid esters are disclosed as unique with respect to their ability to improve the properties of many types of film-forming compositions, including adhesives, floor polishes and non-pigmented epoxy coatings. Additional advantages are obtained when the aforementioned benzoic acid ester is used in combination with the benzoic acid ester of diethylene glycol and/or triethylene glycol.
The data in Example 1 of this patent demonstrate that the leveling and gloss exhibited following six coatings of a floor polish containing the combination of 50 weight percent of 2-ethylhexyl benzoate 33 weight percent of diethylene glycol dibenzoate and 17 weight percent of triethylene glycol dibenzoate was superior to these properties exhibited following six coatings of a polish containing a quantity of 2-ethylhexyl benzoate equal to the weight of the combination of benzoates and none of the glycol esters. When rated for hardness, a film applied using the polish composition containing only the 2-ethylehexyl benzoate was superior.
The present invention is based on the discovery that the leveling of aqueous film-forming compositions, particularly the type employed as polishes for a variety of substrates, including but not limited to including wood, stone and both filled and unfilled organic polymers, together with the gloss, hardness, recoatability and resistance to both soiling and water spotting of the solidified film are maximized using the combination of benzoic acid esters of this invention. The compositions are particularly useful as floor polishes on a variety of flooring materials.